This invention relates to slide projectors and more particularly to the shutter and control mechanism therefor in relation to the presence or absence of a slide.
In using a slide projector, it is desirable for the viewing screen to be unlit during the changing of slides and when there is an empty slide position in the slide tray. To this end, a shutter is incorporated within the projector which blocks the optical path of the projecting light while the projector is indexing between slide positions in the slide tray. Mechanism is also included such that the shutter remains in its blocking position when the projector encounters an empty slide position in the slide tray. U.S. Pat. No. 3,876,298 to Hickey discloses a slide projector having these features wherein a slide clamp, which presses a slide to a slide guide, also senses the absence of a slide and, through suitable linkage, inhibits the opening of the shutter. However, since this mechanism senses the thickness of the slide, the adjustment thereof is highly critical and an unusually thin slide may trip the mechanism.